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We investigate whether the merger announcement dates provided in the Securities Data Corporation (SDC) database are handled correctly by researchers performing event studies. We find that in 24.1% of deals, the popular choice of using the SDC's “Date Announced” field as the event date leads to biased estimates of target firm abnormal returns because of earlier abnormal price movements due to merger-related events such as merger rumors or search-for-buyer types of announcements. We hand collect the merger-related events from news sources and make the complete data set publicly available at the Financial Management website.